In the field of medical technology, various apparatuses are known with which fluids can be withdrawn from patients or fluids can be fed to patients via a hose line. The access to the patient generally takes place with a catheter for introduction into body organs or a cannula for the puncturing of vessels. During the examination or treatment, a correct access to the patient must be ensured. It is therefore necessary to monitor the patient access.
A correct access to the patient is also required particularly for extracorporeal blood treatment apparatuses which comprise an extracorporeal blood circuit. The known extracorporeal blood treatment apparatuses include for example dialysis apparatuses and cell separators, which necessitate an access to the patient's vascular system. In extracorporeal blood treatment, blood is removed from the patient with an arterial puncture cannula via an arterial hose line, the blood being fed back again to the patient with a venous puncture cannula via a venous hose line.
Despite regular monitoring of the vascular access by hospital personnel, there is in principle the risk of the puncture cannula slipping out unnoticed from the patient's blood vessel. The risk of the unnoticed slipping-out of the puncture cannula also exists in the case of home dialysis. Various devices of differing design are known for monitoring the vascular access. The known monitoring devices generally rely on the safety devices present as standard in blood treatment apparatuses, said safety devices triggering immediate interruption of the extracorporeal blood circuit in the case of an incorrect vascular access.
Devices for monitoring a vascular access are known, which comprise a device for detecting moisture in order to be able to detect the issuing of blood at the puncture point. The known devices for detecting moisture for use with the known monitoring devices for the patient access are constituted as a pad which is to be placed on the puncture point. The pad is made from an absorbent material in which a moisture sensor is embedded.
International Patent Publication No. WO 2006/008866 A1, U.S. Patent Application Publication No. 2005/0038325 A1 and U.S. Pat. No. 6,445,304 B1 describe devices for detecting moisture comprising an absorbent material which is placed on the skin. The known pads are characterised in that the moisture sensor is embedded in the absorbent material.
An electrically conductive yarn and a woven fabric comprising the electrically conductive yarn is known from European Patent No. EP 1 537 264 B1. This woven fabric is intended to be used for shielding against electromagnetic fields or for discharging static charges. The woven fabric is also intended to be used for data transmission and current supply. A further intended use of the electrically conductive yarn is to be seen in the production of strain and moisture sensors.
A non-woven fabric of synthetic fibres for shielding against electromagnetic interference sources is described in German Application No. DE 197 12 043 A1. Moreover, woven fabrics comprising a plurality of layers are known, wherein individual points of intersection of warp and weft threads form electrical contact points.
International Patent Publication No. WO 2009/075592 A2 describes a device for detecting moisture in the form of a strip of woven fabric on which or in which two parallel strip conductors are provided, between which the electrical resistance is measured. The two strip conductors are formed by conductive yarns which run only in the longitudinal direction of the strip of woven fabric. Electrical contact points between intersecting strip conductors are not provided. A drawback is that the moisture sensor has only a relatively low sensitivity on account of the form of the electrically conductive structure.